Armature for dynamo electric machines



(No Model.) 2 Sheets-Sheet 1.

L. BELL. ARMATURE FOR DYNAMO ELECTRIC MAGHINES. No. 516,794. Patented Mar. 20, 1894.

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(No Model.) 2 Sheets-Sheet 2.

L. BELL. ARMATURE FOR DYNAMO ELBGTRIG MACHINES. No. 516,794. Patented Mar. 20, 1894'.

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I INVENTEJ UNITED STATES PATENT OFFICE.

LOUIS BELL, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO THE GENERAL ELECTRIC COMPANY, OF SAME PLACE.

ARMATURE FOR DYNAMO-ELECTRIC MACHINES.

SPECIFICATION forming part of Letters Patent No. 516,794, dated March 20,1894.

Application filed March 17,1893. Serial No. 466,399. (No model.)

To to whom it may concern:

Be it known that I, LOUIS BELL, a citizen of the United States, residing at Boston, county of Suffolk, State of Massachusetts, have invented a certain new and useful Improvement in Armatures for Dynamo-Electric Machines, of which the following is a specification.

My invention consists of certain improvements in the construction of armatures for dynamo electric machines.

Its special object is to obviate, so far as may be, the evil eficcts of self-induction in the armatures, which in machines of the direct current type gives rise to troublesome sparking at the commutator, and in machines of the alternating type, to a counter-electro motive force in the armature which cuts down the effective voltage of the machine and so is a feature limiting largely the capacity of the machine. These evils are especially pronounced in machines having armatures of the toothed type in which the coils or windings are disposed in chambers between the teeth, and so are nearly, if not quite, surrounded by magnetic material. For in general the better the local magnetic circuits in the armature around the coils, the greater will be the self induction. With armatures of the smooth faced type it is true the effects of self-induction are not so pronounced, but such an armature lacks many of the characteristic advantages of the toothed construction, among which I may mention as prominent the prevention of eddy currents and the consequent waste of energy, and heating, by leading the magnetic flow through the teeth around the coils rather than directly through them, and the mechanical advantages which the coil chambers present for binding the coils securely in their place and relation upon the armature. From a practical standpoint these advantages are so great that notwith-. standing the fact that the evils of self-induc tion are largely magnified, constructers have been led to adopt the toothed armature very extensively. The present invention retains the toothed type of armature with its characteristic advantages, and at the same time aims to overcome the evils of self-induction ithout undue heating of the core, which results are accomplished in two general ways; by .embedding the coils much less completely than heretofore in magnetic material, and in choking the magnetic lines in the magnetic material with which the coils are surrounded so that it becomes magnetically resistant to a high degree. If the attempt be made in toothed armatures as now constructed to raise the magnetic density in the teeth so as to choke the lines, and in this way render the local magnetic circuits sufficiently resistant tolessen the evils of self-induction, the armature becomes heated, especiallyin alternating current 1na chines where the alternations are of great frequency, and this heating has stood in the way of the practical adoption of the expedient mentioned. But in the present construction the means for ventilating and cooling the teeth are so much improved that the core does not become unduly heated even though the magnetic density in the teeth is made two or three times greater than previous usage has regarded possible. This is accomplished by building up the core of alternate layers of laminae which are of such diameters and of such contours respectively that one set of the layers only has the usual teeth and coilchambers in which the windings are disposed, while the other set of layers is not provided with teeth, but spaces the toothed layers apart, so that the different teeth are separated by air spaces and a large extent of surface is eXposed from which radiation takes place. It is evident that the fewer the laminze in each layer the more will be the number of the teeth, and the greater the radiating surface in any given armature. Hence the best embodiment of the invention will be made by making the layers as many in number as is consistent with the required mechanical strength, but the invention is not limited in this particular to any specific arrangement. As the untoothed layers of laminae do not surround the coils self-induction is for this reason lessened a corresponding amount, and by choking the magnetic lines in the teeth formed in the remaining laminze which do surround the coils, the magnetic resistance thereby gained has the same desired result.

The invention is designed especially for alternating current dynamos and motors, and in such machines it has a special field of usefulness because, the alternations of current being so much more rapid than in direct current machines, and the heat generated correspondingly greater, it has heretofore been deemed impracticable to choke the lines in the teeth to the degree necessary to render them sufficiently resistant to obviate the selfinductive effects. I do not, however, mean to exclude from the invention direct current machines of such kinds that the employment of the means hereinafter described'is found useful.

In theaccompanying drawings, Figure 1 is a side view of a portion of an armature sufficient to illustrate the invention. Fig. 2 is a sectional view taken on line w-m Fig. 1. Fig. 3 is a side view showing a modified form of winding. Fig. 4 is a side view showing a further feature of the invention. Fig. 5- is a face view of the armature core. Fig. 6 is a detail of one of the air deflecting vanes, and Flg. Z shows a modified form which may be given to the laminae.

The machine illustrated-isa multipolarmachine of the alternating type, and except in the specific features described resembles the designs now in common use.

The, poles of the field magnet are represented at A, and B. is a part of the armature core. The armature is built up of laminae in the ordinary manner, which laminae may either be rings made in a single piece or of interlocking sections which fit together to form rings when the core is completed. The core is built upof successive layers of these laminae which alternate with one another as seen in Fig. 2, and are of different diameters and contours, one set of layers E being of greater diameter and having teeth. 6 forming coil chambers in which the coils or windings G are arranged, while the other set of layers D are of lesser diameter, have no teeth, and so do not surround the coils as do the layers E. The coils G are insulated from the core, and: are held in place by an insulating wedge H in the ordinary manner. They may consist of wire wound in strands as in Fig. 1, or bars of conducting material asin Fig. 3. The difference between this construction and prior armatures is thatinstead of solid single teeth formed on and extending across the face of the core, the teeth are split up into individual portions forming, as it were, a row of teeth each separated from its neighbor in the row by an air space, and each consisting of a relatively small number of laminae so that the extent of radiating surface is im- 6 o mensely increased.

In Figs. 4 and 5 the same parts already described are shown, but the desired results aimed at by the invention are still further enhanced by special means for ventilating the individual teeth. It is customary in armatures of this character to sub-divide the core into a number of parallel sections sepathe adjacent core sections.

rated. by ventilating openings through which the air is forced asthe armature rotates. The ordinary escape openings between the core sections are closed up by vanes I, which consist of castings shaped as shown in Fig. 6 so that the top flange .I closes thespace between As shown in this figure the toothed laminae E are notched or channeled at 9 so as to form open passageways beneath the coils, and the smooth faced laminae D are so arranged that the circumference bounded by them is somewhat below the coils as shown by the dotted line L so that the passage-ways 9 all communicate with one another through the difierent spaces between the teeth. Now as the armature rotates the currents. of air instead ofpassing directly up between the sections as heretofore are deflected into the passageways g and thence pass out between the difierent toothed layers oflaminee afiording a very thorough ventilation for them all. It is tobe observed also that sinking the untoothed laminae D below the coils keeps them entirely out of contact with the coils, and so reduces somewhat further self-induction.

In Fig. 5 the construction of the core, is

shown with the coils in place. 0, 0., O are three different armature sections spaced apart in the ordinary manner, but as already explained the vanes I close the usual openings and cause the air to sift out around and between the different toothed layers, forming the core.

In Fig. 7 it is shown that the laminae Dinstead of being entirely smooth faced may chine having a core built up of layers of laminae arranged side by side, and alternating with other layers of laminae of greater diameter, and provided with teeth forming coil chambers whose depth is substantially equal to the distance the toothed laminae project beyond the intermediate laminae.

2. An armature for a dynamo. electric machine havinga. core consisting of alternate layers of laminae of diiferent sizes and contours respectively, one set of layers presenting chambers for the coils and having teeth to a large extent surrounding the coils, while the intermediate layers have no such teeth surrounding the coils, as described.

3. An armature for dynamo electric machines provided with laminated teeth, the

' laminae arranged in groups separated by ventilating spaces.

4. -An armature for a dynamo electricv ma chine having a core divided into sections separated by ventilating openings, said core consisting of alternating layers of toothed and untoothed laminae, as described, and vanes closing the usual openings between the sections and deflecting currents of air around 5 and between the teeth on the core, as described.

5. An armature for a dynamo electric machine having a core divided into sections with intermediate ventilating openings, said [0 core consisting of alternate layers of toothed laminze presenting chambers for the coils and and having passage-ways extending across the core beneath the coils, and intermediate layers of laminae of lesser diameter and arranged sothatthepassage-wayscommunicatethrough 15 the spaces between the teeth, as described.

In witness whereof I have hereunto set my hand this 15th day of March, 1893.

LOUIS BELL. Witnesses:

W. H. BENTLEY, A. O. ORNE. 

